Metal roof decking, usually but not exclusively corrugated, is employed in many commercial buildings and storage buildings as well as some residential buildings. Most metal decks are paddle welded to the underlying structure. Welding is inconsistent and weak. It is also subject to rust and corrosion because it burns the protective coating off both sides of the steel decking at its interface. Recently some metal roof decking material is affixed by fasteners such as screws. To spread to a larger surface area any load placed on the roof deck by the screw head during wind uplift or similar events, a flat washer has commonly been placed under the screw head. While this does indeed spread some of the load of the screw, it also causes a point stress especially in corrugated decking material. This point stress is created where the flat washer intersects the curved corrugation.
Roof failures have occurred due to penetration of the roof deck at these point stress points during wind uplift and consequent tearing of the roof decking from the penetration point around the fasteners. This of course leads to an easy undesired removal of the roof assembly after sufficient fastening points have been compromised causing extreme deck deflection in high winds.